Sensors that estimate the current flowing in a conductor by sensing the related magnetic field are known in the art. In as typical arrangement, the magnetic field sensor is fixedly positioned near the conductor such that it can sense the magnetic field related to current flowing in the conductor. To be accurate, the configuration of the conductor and the positional relationship between the conductor and the sensor must be known precisely. In practice, the latter is to challenge because small position errors result in large current measurement errors. Referring to FIG. 1, a sensor 100 having two magnetic field sensing elements 102, such as Hall plates, is depicted relative to a conductor 104. Sensing elements 102 are sensitive to magnetic fields in the y-direction, or By fields. Errors in a vertical or y-direction as depicted have a larger impact on sensor accuracy than those in a lateral or x-direction. Errors in the y-direction can be related to, for example, varying thickness of a mold compound, glue or bonding material between the sensor and the conductor.
Conventional techniques used to calibrate the sensor to account for positioning variances typically involve coupling the sensor and conductor, applying a known current to the conductor and measuring the current by the sensor. The values of the known current and measured current can then be used to determine a sensitivity of the sensor, which can be programmed into the sensor and taken into account going forward when currents are measured. It is challenging, however, to generate a stable known current for such a procedure.
Therefore, there is a need for improved current sensors.